Allow roast to sit at room temperature for 30 minutes. Season on both sides generously with salt and pepper. Preheat a cast iron skillet over high heat with 2 tbsp butter. Sear each side of the roast for 3-4 minutes until a crispy brown crust forms (remember to get the edges, too).
I your slow cooker, add roast, beef broth, Worcestershire sauce, parsley, and remaining liquid from the seared roast. Add lid and cook on low for 7 hours.
Add yellow and green onions to the slow cooker. Stir into the liquid and cook for one more hour.
Allow rib roast to rest on a cutting board for 10 minutes. Slice thinly against the grain and off the bone.
For the rolls, preheat the oven to 400 degrees. Melt 2 tbsp butter and stir in minced garlic. Brush mixture onto both sides of the ciabatta halves and add a slice of provolone on top. Cook for 5 to 8 minutes until lightly browned and crispy.
To make the dressing, stir together all dressing ingredients until well-blended. It should have a somewhat thick consistency, but still be thin enough to drizzle. Add salt and pepper to taste.
To assemble a sandwich, layer a few roast slices on top of the cheese. Spoon onions and some of the cooking liquid over the steak. Drizzle dressing over the sandwich.